The present invention relates to cleaners for photographic equipment and for other apparatus which comes into contact with photographic emulsions, photographic developer solutions, used photographic film, and so forth. The invention is particularly useful in cleaning developer racks from photographic processing equipment, and for cleaning tanks holding developer solutions, for example. It is now common for exposed photographic film to be developed using automated or semi-automated equipment whereby the exposed film is fed through a series of racks fitted with rollers. This system is used in developing normal photographic film, as well as in developing medical X-ray film, and in specialist printing and graphic arts photography.
In general, the system of developing exposed film comprises a series of three racks fitted with rollers, each rack sitting inside a tank. The film winds between the rollers, so that it can be drawn through the various liquids in the tanks, in series. The first tank normally contains a photographic developer solution. The second tank containing a roller rack normally contains photographic fixer solution, and the last rack, known as the wash rack, is located in a water-filled tank.
The first rack, in the developer solution, accumulates residues from the photographic film which passes through the developer solution, and this rack requires special cleaning on a periodic basis. Typically the rack must be cleaned monthly or quarterly, depending on the throughput of film, for instance.
In order to clean the rack, a cleaning solution is required, and in the past, the commercial cleaning system which has most often been used involves the use of an aqueous solution of a strong oxidising agent, particularly potassium dichromate, and sulfamic acid. Potassium dichromate (K.sub.2 Cr.sub.2 O.sub.7) is a strong oxidising agent, and sulfamic acid (H.sub.2 NSO.sub.3 H) assists in cleaning the equipment, and acidifies the mixture. Chromium salts, such as potassium dichromate, can be dangerous to users, and are also enviromentally harmful, being difficult to dispose of, and chromium salts also cause problems in waste treatment plants.
In addition, the residue to be cleaned includes silver, and the dichromate cleaning mixture keeps the silver in solution, making it difficult to recover as a useful material for recycling, or else the cleaning procedure may allow some silver to be lost in the waste that is produced.
Also, the prior art potassium dichromate cleaning system is normally used at a temperature of about 30.degree.-40.degree. C. The dichromate concentrate is usually sold as a powder, and when used, the operator will normally make up a 4 to 5 litre concentrated solution which is poured over the rack to be cleaned and into the tank, and then the tank topped up by the addition of further hot water. In water at room temperature the powder is normally difficult to dissolve, and as well the higher temperature accelerates the cleaning ability of the dichromate solution.
It would therefore be of benefit if a cleaning solution for developer racks and the like could be developed which avoids the use of chromate compounds, and which preferably also may perform well as a cleaner in cold water as well as in hot water.